The dry gas seals have wide applications in the conditions of high temperature,high pressure and a variety of corrosive media,but it has been not enough to understand the effects of high pressure and high temperature on dry gas seals,especially the problems in the numerical simulation.Both pressure and temperature of end-face gas film field in dry gas seals change greatly,especially at the working condition of high pressure.The density and viscosity of sealing medium or nitrogen change with varying pressure and temperature.Especially,the effect of pressure on the former is greater.In usual numerical simulation for dry gas seals,the density of sealing medium is determined according to the given temperature and pressure,which does not take into account the influences of physical parameters of sealing medium on seal performance so that the results might have errors.A new way used for the simulation of flow field of high pressure dry gas seals was proposed with the consideration of the effects of the changes of flow field and temperature field on the density of sealing medium in order to decrease the errors.Firstly,ANSYS Workbench software was used to make a thermal analysis for sealing rings to obtain the temperature field.The temperature distribution in the gas film field was then estimated by CFD.Then,user defined functions(UDFs) were created to relate the density of nitrogen (sealing medium) to pressure and temperature.Fluent software was used to complete the simulation with UDF loaded.Pressure distribution of end-face gas field and the opening force of the seal were obtained after continuous iteration.The flow fields of high pressure dry gas seals were reflected more truly.The flow fields of a dry gas seal were simulated using Fluent soft ware by the methods of variable-density (to define the density as a function of pressure and temperature) and the given density (to take density as the given directly),respectively.The grid size independent verification was carried out.The comparison of simulation results showed that the variable-density method could make the results closer to the conditions of the actual situation.It is feasible to use UDFs of Fluent to describe the variable-density of gas film between the sealing faces of a dry gas seal,which provides a new method to more accurately simulate gap flow field between sealing faces.The effect of pressure on the density of sealing gas is great under high pressure.The flow fields of high pressure dry gas seals are reflected more truly by the methods of variable-density.Moreover,the influence of temperature change on the density of sealing gas should be taken into account.
